Anatomy & Physiology of Cardiac system with Cardiac Assessment- Diagnostic Investigation

ANATOMY AND PHYSIOLOGY OF THE CARDIOVASCULAR SYSTEM
Dr. Pallavi Pathania.
Ph.D , MSN.

HEART
LOCATED ON THE DIAPHRAGM
NEAR THE MIDLINE OF THE THORACIC CAVITY

7
Overview
The right side receives oxygen-
poor blood from the body and
tissues and then pumps it to the
lungs to pick up oxygen and dispel
carbon dioxide
Its left side receives oxygenated
blood returning from the lungs
and pumps this blood throughout
the body to supply oxygen and
nutrients to the body tissues
The heart=a muscular double pump with 2 functions

8
Heart’s position in thorax
In mediastinum – behind sternum and pointing left, lying on
the diaphragm
It weighs 250-350 gm (about 1 pound)
Feel your heart beat at apex
(this is of a person lying down)

9
Location and Surface Projection
The heart is hollow, cone-shaped,
about the size of a closed fist .
Lies in the mediastinum between
the lungs and rests upon the
diaphragm
Two-thirds of its mass lies to the
left of the midline
Apex - lower, pointed end
Base - broader, superior portion

10
Heart’s position in thorax

11
Layers of Heart Wall
Pericardium - membrane (sac) that surrounds and protects the
heart, it has two layers:
(a) Fibrous pericardium - superficial layer, tough, inelastic,
prevents overstretching, provides protection, and anchors the
heart in place
(b) Serous pericardium - deeper layer, thin;
(i) parietal layer - fused to the fibrous pericardium, and (ii)
visceral layer (or epicardium) adheres to the heart itself
Pericardial cavity (between the two layers) is filled with
pericardial fluid which reduces friction.

FIBROUS:THIN INELASTIC, DENSE IRREGULAR
CONNECTIVE TISSUE
---HELPS IN PROTECTION, ANCHORS HEART TO
MEDIASTINUM
SEROUS: THINNER, MORE DELICATE DIVIDED INTO
PARIETAL AND VISCERAL
14

EPICARDIUM: COMPOSED OF MESOTHELIUM AND
DELICATE CONNECTIVE TISSUE (IMPARTS A SLIPPERY
TEXTURE TO THE OUTER SURFACE OF THE HEART).

MYOCARDIUM:RESPONSIBLE FOR PUMPING
ENDOCARDIUM: THIN LAYER OF ENDOTHELIUM
WHICH IS CONTINOUS WITH THE LINING OF THE
LARGE BLOOD VESSELS ATTACHED TO THE HEART.
16

18
Chambers of the heart
Two atria
Right atrium
Left atrium
Two ventricles
Right ventricle
Left ventricle
--------------------------------------------------------------------------------

19
Chambers of the heart
divided by septae:
Two atria-divided by
interatrial septum
Right atrium
Left atrium
Two ventricles-divided by
interventricular septum
Right ventricle
Left ventricle

20
Myocardial Thickness and Function
The atria are thin-walled as they deliver blood under less
pressure
The ventricles have thick walls since they pump blood at a
higher pressure and over greater distances
The right and left ventricles eject equal amounts of blood
The left ventricle is thicker because it pumps under higher
pressure and over a greater distance than the right ventricle
(Fig. 14.4c)

ATRIOVENTRICULAR &
SEMILUNAR VALVES

22
Heart Valves - Atrioventricular
The four valves prevent backflow of blood in the heart after
blood passes through them
Atrioventricular (AV) valves
- tricuspid valve between the right atrium and the right
ventricle
- bicuspid (mitral) valve - between the left atrium
and the left ventricle
 Chordae tendineae and associated papillary muscles permit
flow but prevent backflow

23
Heart Valves - Semilunar
Two semilunar (SL) valves each having three semilunar
cusps
Allow ejection of blood from the ventricles into the
pulmonary trunk and aorta
Prevent backflow of blood into the heart
Pulmonary valve - between the pulmonary trunk and the
right ventricle
Aortic valve - between the aorta and the left ventricle

SYSTEMIC AND PULMONARY
CIRCULATION
LEFT SIDE IS A PUMP
TO THE SYSTEMIC
CIRCULATION.
RIGHT SIDE IS A PUMP
TO THE PULMONARY
CIRCULATION.

27
Circulation of Blood
The heart pumps blood into two circuits arranged in series
(connected end to end)
Systemic circulation - left side of heart receives
oxygenated blood from the lungs
Pumps this blood into the aorta which branches into
systemic arteries that carry blood to all organs except
alveoli of the lungs
Arteries branch into arterioles and eventually into
systemic capillaries where nutrients, gases, wastes, etc.
are exchanged with the surrounding cells; venules and
subsequently systemic veins return the deoxygenated
blood to the right atrium

28
Circulation of Blood
Pulmonary circulation - the right ventricle pumps blood
into the pulmonary trunk which branches into the
pulmonary arteries
This blood goes to the pulmonary capillaries where the
blood becomes oxygenated
Pulmonary veins carry the oxygenated blood to the left
atrium

30
Coronary (Cardiac) Circulation
Two coronary arteries, the left and right coronary
arteries branching from the ascending aorta supply the
myocardium
Left coronary artery divides into the anterior
interventricular branch (or left anterior descending
artery) and the circumflex branch
Right coronary artery divides into the posterior
interventricular branch and marginal branch

34
Cardiac Conduction System
Sinoatrial (SA) node - the heart’s natural pacemaker,
initiates each heartbeat
Other components of of the conduction system include:
Atrioventricular (AV) node, Atrioventricular
bundle or bundle of His, right and left bundle
branches, Purkinje fibers
The nervous system and certain hormones can alter the pace
of contractions but the nervous system does not initiate
contractions

35
Electrical conduction system:
specialized cardiac muscle cells that carry
impulses throughout the heart
musculature, signaling the chambers to
contract in the proper sequence

38
Conduction system
SA node (sinoatrial)
In wall of RA
Sets basic rate: 70-80
Is the normal pacemaker
Impulse from SA to atria
Impulse also to AV node via internodal pathway
AV node
In interatrial septum

39
Conduction continued
SA node through AV bundle (bundle of His)
Into interventricular septum
Divides
R and L bundle branches
become subendocardial
branches (“Purkinje
fibers”)
Contraction begins
at apex

ATRIAL SYSTOLE
LASTS FOR 0.1 SEC
ATRIAL DEPOLARIZATION CAUSES ATRIAL
SYSTOLE
IT CONTRIBUTES A FINAL 25mL OF BLOOD
TO EACH VENTRICLE
END OF ATRIAL SYSTOLE IS ALSO END OF
VENTRICULAR DIASTOLE
END-DIASTOLIC VOLUME IS 130 mL

VENTRICULAR SYSTOLE
LASTS FOR 0.3 SEC
IT IS CAUSED BY VENTRICULAR
DEPOLARIZATION
ISOVOLUMETRIC CONTRACTION LASTS
FOR 0.05 SECONDS WHEN BOTH THE
SEMILUNAR AND ATRIOVENTRICULAR
VLAVES ARE CLOSED.

THE SL VALVES OPEN WHEN
-THE LEFT VENTRICULAR PRESSURES SURPASSES AORTIC
PRESSURE(80 MM OF MERCURY)
-THE RIGHT VENTRICULAR PRESSURE RISES ABOVE
PULMONARY PRESSURE (20 mmHg)
SL VALVES OPEN FOR 0.25 SEC

THE LEFT VENTRICLE EJECTS ABOUT 70 ML INTO
THE AORTA
THE RIGHT VENTRICLE EJECTS THE SAME VOLUME
INTO THE PULMONARY TRUNK.
END SYSTOLIC VOLUME IS 60mL IN EACH
VENTRICLE .

Assessment of functions of heart
and vascular system

HEART SOUNDS
PRODUCED FROM BLOOD
TURBULENCE CAUSED BY
CLOSING OF HEART VALVES
S1 – ATRIOVENTRICULAR VALVE
CLOSURE
S2 – SEMILUNAR VALVE CLOSURE
S3- RAPID VENTRICULER FILLING
S4- ATRIAL SYSTOLE

CARDIAC OUTPUT
CO = SV X HR
FOR A RESTING ADULT
CO = 70mL/beat x75beats/min
= 5250 mL/min
= 5.25 L/min
mL/min mL/beat (Beats/min)

HEMODYNAMIC MONITORING OF HEART

Hemodynamic monitoring refers to measurement of pressure,
flow and oxygenation of blood within the cardiovascular system.
Hemodynamic monitoring measures the blood pressure
inside the veins, heart, and arteries. It also measures blood
flow and how much oxygen is in the blood. It is a way to see
how well the heart is working.
Hemodynamic monitoring plays an important role in
the management of today's acutely ill patient. ...
Current hemodynamic monitoring therefore includes
measurement of heart rate, arterial pressure, cardiac filling
pressures or volumes, cardiac output, and mixed venous
oxygen saturation (SvO2).

WHAT IS HEMODYNAMIC MONITORING?
Hemodynamic monitoring measures the blood pressure inside the veins, heart, and arteries.
It also measures blood flow and how much oxygen is in the blood. It is a way to see how
well the heart is working.
WHEN IS IT DONE?
Many treatments depend on seeing small changes in the way the heart is working. These
changes happen first deep inside the body. It may take time for these changes to show at the
body surface, where they can be observed more easily. Hemodynamic monitoring can detect
these changes early by testing samples of blood from deep inside the body.
Hemodynamic monitoring helps your healthcare provider know if you will need blood or
fluid transfusions. It shows whether the lungs are getting enough oxygen. It checks how well
the heart is pumping by measuring the total blood flow per minute.
This test may be done, for example, if you are in intensive care recovering from a heart
attack or if you have fluid around your heart.

Pulmonary Artery Pressure (PAP) - Hemodynamic Monitoring
- Getting Started. Hemodynamic Monitoring - The pulmonary
artery pressure (PAP) is generally 25/10 mm Hg (since the
pulmonary vasculature is normally low resistance system). The
pulmonary artery pressure (PAP) is helpful in diagnosing many
clinical conditions.
The primary hemodynamic parameters include heart rate
(HR) and blood pressure (BP), while the advanced
hemodynamic parameters include stroke volume (SV),
cardiac output (CO), and total peripheral resistance (TPR) [14].

 Central venous pressure is a measure of pressure in the superior vena cava which can be
used as an estimation of preload and right atrial pressure. Central venous pressure is
often used as an assessment of hemodynamic in a patient, particularly in intensive care
units. The central venous pressure can be measured using a central venous catheter
placed in the superior vena cava near the right atrium. A normal central venous pressure
reading is between 8 to 12 mmHg. This value can be changed depending on a patient’s
volume status or venous compliance.
 Central venous pressure (CVP), an estimate of right atrial pressure, has been used to
assess cardiac preload and volume status in critically ill patients, assist in the diagnosis of
right-sided heart failure, and guide fluid resuscitation. It is determined by the
interaction between cardiac function and venous return. CVP measurements are
relatively easy to obtain; however, because of the complex relationship between CVP,
cardiac output, and the vascular system, they may be difficult to interpret.

The central venous pressure (CVP) is the
pressure measured in the central veins close to the heart. It
indicates mean right atrial pressure and is frequently used as
an estimate of right ventricular preload. The CVP
does not measure blood volume directly, although it is
often used to estimate this.
Pulmonary blood pressure is normally a lot lower than
systemic blood pressure. Normal pulmonary
artery pressure is 8-20 mm Hg at rest. If the pressure in the
pulmonary artery is greater than 25 mm Hg at rest or 30 mmHg
during physical activity, it is abnormally high and is
called pulmonary hypertension.

Chest x-ray uses a very small dose of ionizing radiation to
produce pictures of the inside of the chest. It is used to
evaluate the lungs, heart and chest wall and may be used to
help diagnose shortness of breath, persistent cough, fever,
chest pain or injury. It also may be used to help diagnose and
monitor treatment for a variety of lung conditions such as
pneumonia, emphysema and cancer. Because chest x-ray is
fast and easy, it is particularly useful in emergency diagnosis
and treatment.

 X-rays are a form of radiation like light or radio waves. X-rays pass through
most objects, including the body. Once it is carefully aimed at the part of the
body being examined, an x-ray machine produces a small burst of radiation that
passes through the body, recording an image on photographic film or a special
detector.
 Different parts of the body absorb the x-rays in varying degrees. Dense bone
absorbs much of the radiation while soft tissue, such as muscle, fat and organs,
allow more of the x-rays to pass through them. As a result, bones appear white
on the x-ray, soft tissue shows up in shades of gray and air appears black.
 On a chest x-ray, the ribs and spine will absorb much of the radiation and
appear white or light gray on the image. Lung tissue absorbs little radiation and
will appear dark on the image.
 Until recently, x-ray images were maintained on large film sheets (much like a
large photographic negative). Today, most images are digital files that are
stored electronically. These stored images are easily accessible for diagnosis and
disease management.

 Magnetic resonance imaging (MRI) is a type of scan that uses strong
magnetic fields and radio waves to produce detailed images of the inside of
the body.
 An MRI scanner is a large tube that contains powerful magnets. You lie inside the tube
during the scan.
 An MRI scan can be used to examine almost any part of the body, including the:
 brain and spinal cord
 bones and joints
 breasts
 heart and blood vessels
 internal organs, such as the liver, womb or prostate gland
 The results of an MRI scan can be used to help diagnose conditions, plan treatments and
assess how effective previous treatment has been.

 Most of the human body is made up of water molecules, which consist of hydrogen and
oxygen atoms.
 At the centre of each hydrogen atom is an even smaller particle called a proton. Protons
are like tiny magnets and are very sensitive to magnetic fields.
 When you lie under the powerful scanner magnets, the protons in your body line up in
the same direction, in the same way that a magnet can pull the needle of a compass.
 Short bursts of radio waves are then sent to certain areas of the body, knocking the
protons out of alignment.
 When the radio waves are turned off, the protons realign. This sends out radio signals,
which are picked up by receivers.
 These signals provide information about the exact location of the protons in the body.
 They also help to distinguish between the various types of tissue in the body, because
the protons in different types of tissue realign at different speeds and produce distinct
signals.
 In the same way that millions of pixels on a computer screen can create complex
pictures, the signals from the millions of protons in the body are combined to create a
detailed image of the inside of the body.

NMRI { Nuclear magnetic resonance imaging.}

Cardiac stress test/
TRADE MILL STRESS TESTING

 A stress test, also called an exercise stress test, shows how your heart works
during physical activity. Because exercise makes your heart pump harder and
faster, an exercise stress test can reveal problems with blood flow within your
heart.
 A stress test usually involves walking on a treadmill or riding a stationary bike
your heart rhythm, blood pressure and breathing are monitored. Or you'll
receive a drug that mimics the effects of exercise.
 Doctor may recommend a stress test if you have signs or symptoms of
coronary artery disease or an irregular heart rhythm (arrhythmia). The test may
also guide treatment decisions, measure the effectiveness of treatment or
determine the severity if you've already been diagnosed with a heart condition.

 Bronchoscopy is a procedure that lets doctors look at your lungs and air
passages. It's usually performed by a doctor who specializes in lung disorders (a
pulmonologist). During bronchoscopy, a thin tube (bronchoscope) is passed
through your nose or mouth, down your throat and into your lungs.
 Bronchoscopy is most commonly performed using a flexible bronchoscope.
However, in certain situations, such as if there's a lot of bleeding in your lungs
or a large object is stuck in your airway, a rigid bronchoscope may be needed.
 Common reasons for needing bronchoscopy are a persistent cough, infection or
something unusual seen on a chest X-ray or other test.
 Bronchoscopy can also be used to obtain samples of mucus or tissue, to remove
foreign bodies or other blockages from the airways or lungs, or to provide
treatment for lung problems.

 Bronchoscopy is usually done to find the cause of a lung problem. For example, your
doctor might refer you for bronchoscopy because you have a persistent cough or an
abnormal chest X-ray.
 Reasons for doing bronchoscopy include:
 Diagnosis of a lung problem
 Identification of a lung infection
 Biopsy of tissue from the lung
 Removal of mucus, a foreign body, or other obstruction in the airways or lungs, such as
a tumor
 Placement of a small tube to hold open an airway (stent)
 Treatment of a lung problem (interventional bronchoscopy), such as bleeding, an
abnormal narrowing of the airway (stricture) or a collapsed lung (pneumothorax)
 During some procedures, special devices may be passed through the bronchoscope, such
as a tool to obtain a biopsy, an electrocautery probe to control bleeding or a laser to
reduce the size of an airway tumor. Special techniques are used to guide the collection
of biopsies to ensure the desired area of the lung is sampled.
 In people with lung cancer, a bronchoscope with a built-in ultrasound probe may be
used to check the lymph nodes in the chest. This is called endobronchial ultrasound
(EBUS) and helps doctors determine the appropriate treatment. EBUS may be used for
other types of cancer to determine if the cancer has spread.

 Pulmonary function tests (PFTs) are non invasive tests that show how well the lungs are
working. The tests measure lung volume, capacity, rates of flow, and gas exchange.
This information can help your healthcare provider diagnose and decide the treatment of
certain lung disorders.
 There are 2 types of disorders that cause problems with air moving in and out of the lungs:
 Obstructive. This is when air has trouble flowing out of the lungs due to airway resistance.
This causes a decreased flow of air.
 Restrictive. This is when the lung tissue and/or chest muscles can’t expand enough. This
creates problems with air flow, mostly due to lower lung volumes.
 PFT can be done with 2 methods. These 2 methods may be used together and perform different
tests, depending on the information that your healthcare provider is looking for:
 Spirometry. A spirometer is a device with a mouthpiece hooked up to a small electronic
machine.
 Plethysmography. You sit or stand inside an air-tight box that looks like a short, square
telephone booth to do the tests.
 PFT measures:
 Tidal volume (VT). This is the amount of air inhaled or exhaled during normal breathing.
 Minute volume (MV). This is the total amount of air exhaled per minute.
 Vital capacity (VC). This is the total volume of air that can be exhaled after inhaling as much
as you can.

 Functional residual capacity (FRC). This is the amount of air left in lungs after exhaling
normally.
 Residual volume. This is the amount of air left in the lungs after exhaling as much as you can.
 Total lung capacity. This is the total volume of the lungs when filled with as much air as
possible.
 Forced vital capacity (FVC). This is the amount of air exhaled forcefully and quickly after
inhaling as much as you can.
 Forced expiratory volume (FEV). This is the amount of air expired during the first, second,
and third seconds of the FVC test.
 Forced expiratory flow (FEF). This is the average rate of flow during the middle half of the
FVC test.
 Peak expiratory flow rate (PEFR). This is the fastest rate that you can force air out of your
lungs.
 Normal values for PFTs vary from person to person. The amount of air inhaled and exhaled in your
test results are compared to the average for someone of the same age, height, sex, and race. Results
are also compared to any of your previous test results. If you have abnormal PFT measurements or
if your results have changed, you may need other tests.

 Electrocardiography is the process of producing an electrocardiogram (ECG or EKG), a
recording - a graph of voltage versus time - of the electrical activity of the heartusing electrodes
placed on the skin.
 These electrodes detect the small electrical changes that are a consequence of cardiac muscle
depolarization followed by repolarization during each cardiac cycle (heartbeat). Changes in the
normal ECG pattern occur in numerous cardiac abnormalities, including cardiac rhythm
disturbances (such as atrial fibrillation and ventricular tachycardia), inadequate coronary artery
blood flow (such as myocardial ischemia and myocardial infarction), and electrolyte disturbances
(such as hypokalemia and hyperkalemia).
 In a conventional 12-lead ECG, ten electrodes are placed on the patient's limbs and on the
surface of the chest. The overall magnitude of the heart's electrical potential is then measured
from twelve different angles ("leads") and is recorded over a period of time (usually ten
seconds). In this way, the overall magnitude and direction of the heart's electrical depolarization
is captured at each moment throughout the cardiac cycle.
 There are three main components to an ECG: the P wave, which represents the depolarization of
the atria; the QRS complex, which represents the depolarization of the ventricles; and the
T wave, which represents the repolarization of the ventricles.

 During each heartbeat, a healthy heart has an orderly progression of depolarization that
starts with pacemaker cells in the sinoatrial node, spreads throughout the atrium, passes
through the atrioventricular node down into the bundle of His and into the
Purkinje fibers, spreading down and to the left throughout the ventricles.
 This orderly pattern of depolarization gives rise to the characteristic ECG tracing. To
the trained clinician, an ECG conveys a large amount of information about the structure
of the heart and the function of its electrical conduction system.
 Among other things, an ECG can be used to measure the rate and rhythm of heartbeats,
the size and position of the heart chambers, the presence of any damage to the heart's
muscle cells or conduction system, the effects of heart drugs, and the function of
implanted pacemakers

Electrodes are the actual conductive pads attached to the body surface.Any pair of electrodes
can measure the electrical potential difference between the two corresponding locations of
attachment. Such a pair forms a lead. However, "leads" can also be formed between a physical
electrode and a virtual electrode, known as the Wilson's central terminal, whose potential is
defined as the average potential measured by three limb electrodes that are attached to the
right arm, the left arm, and the left foot, respectively.
Commonly, 10 electrodes attached to the body are used to form 12 ECG leads, with each lead
measuring a specific electrical potential difference (as listed in the table below).[22]
Leads are broken down into three types: limb; augmented limb; and precordial or chest. The 12-
lead ECG has a total of three limb leads and three augmented limb leads arranged like spokes
of a wheel in the coronal plane (vertical), and six precordial leads or chest leads that lie on the
perpendicular transverse plane (horizontal).
In medical settings, the term leads is also sometimes used to refer to the electrodes
themselves, although this is technically incorrect. This misuse of terminology can be the source
of confusion. The 10 electrodes in a 12-lead ECG are listed below.
Two types of electrodes in common use are a flat paper-thin sticker and a self-adhesive circular
pad. The former are typically used in a single ECG recording while the latter are for continuous
recordings as they stick longer. Each electrode consists of an electrically conductive electrolyte
gel and a silver/silver chlorideconductor The gel typically contains potassium chloride –
sometimes silver chloride as well – to permit electron conduction from the skin to the wire and to
the electrocardiogram.
The common virtual electrode, known as the Wilson's central terminal (VW
), is produced by
averaging the measurements from the electrodes RA, LA, and LL to give an average potential
of the body:
In a 12-lead ECG, all leads except the limb leads are unipolar (aVR, aVL, aVF, V1
, V2
, V3
, V4
, V5
,
and V6
). The measurement of a voltage requires two contacts and so, electrically, the unipolar
leads are measured from the common lead (negative) and the unipolar lead (positive). This
averaging for the common lead and the abstract unipolar lead concept makes for a more
challenging understanding and is complicated by sloppy usage of "lead" and "electrode".

Electrode name Electrode placement
RA On the right arm, avoiding thick muscle.
LA
In the same location where RA was placed, but on the
left arm.
RL
On the right leg, lower end of inner aspect of
calf muscle. (Avoid bony prominences)
LL
In the same location where RL was placed, but on the
left leg.
V1
In the fourth intercostal space (between ribs 4 and 5)
just to the right of the sternum (breastbone).
V2
In the fourth intercostal space (between ribs 4 and 5)
just to the left of the sternum.
V3 Between leads V2 and V4.
V4
In the fifth intercostal space (between ribs 5 and 6) in
the mid-clavicular line.
V5
Horizontally even with V4, in the left
anterior axillary line.
V6
Horizontally even with V4 and V5 in the
mid-axillary line.

Background grid
ECGs are normally printed on a grid. The horizontal axis represents time and the vertical axis represents
voltage. The standard values on this grid are shown in the adjacent image:
•A small box is 1 mm × 1 mm and represents 0.1 mV × 0.04 seconds.
•A large box is 5 mm × 5 mm and represents 0.5 mV × 0.20 seconds.
The "large" box is represented by a heavier line weight than the small boxes.
Not all aspects of an ECG rely on precise recordings or having a known scaling of amplitude or time. For
example, determining if the tracing is a sinus rhythm only requires feature recognition and matching, and not
measurement of amplitudes or times (i.e., the scale of the grids are irrelevant). An example to the contrary,
the voltage requirements of left ventricular hypertrophy require knowing the grid scale.

Rate and rhythm[edit]
In a normal heart, the heart rate is the rate in which the sinoatrial node depolarizes as it is the source
of depolarization of the heart. Heart rate, like other vital signs like blood pressure and respiratory rate,
change with age. In adults, a normal heart rate is between 60 and 100 bpm (normocardic) where in
children it is higher. A heart rate less than normal is called bradycardia (<60 in adults) and higher than
normal is tachycardia (>100 in adults). A complication of this is when the atria and ventricles are not in
synchrony and the "heart rate" must be specified as atrial or ventricular (e.g., the ventricular rate in
ventricular fibrillation is 300–600 bpm, whereas the atrial rate can be normal [60–100] or faster [100–
150]).
In normal resting hearts, the physiologic rhythm of the heart is normal sinus rhythm (NSR). Normal
sinus rhythm produces the prototypical pattern of P wave, QRS complex, and T wave. Generally,
deviation from normal sinus rhythm is considered a cardiac arrhythmia. Thus, the first question in
interpreting an ECG is whether or not there is a sinus rhythm. A criterion for sinus rhythm is that P
waves and QRS complexes appear 1-to-1, thus implying that the P wave causes the QRS complex.
Once sinus rhythm is established, or not, the second question is the rate. For a sinus rhythm this is
either the rate of P waves or QRS complexes since they are 1-to-1. If the rate is too fast then it is
sinus tachycardia and if it is too slow then it is sinus bradycardia.
If it is not a sinus rhythm, then determining the rhythm is necessary before proceeding with further
interpretation. Some arrhythmias with characteristic findings:
Absent P waves with "irregularly irregular" QRS complexes is the hallmark of atrial fibrillation
A "saw tooth" pattern with QRS complexes is the hallmark of atrial flutter
Sine wave pattern is the hallmark of ventricular flutter
Absent P waves with wide QRS complexes and a fast heart rate is ventricular tachycardia
Determination of rate and rhythm is necessary in order to make sense of further interpretation.

 Interpretation of the ECG is fundamentally about understanding the
electrical conduction system of the heart. Normal conduction starts and
propagates in a predictable pattern, and deviation from this pattern can be a
normal variation or be pathological. An ECG does not equate with mechanical
pumping activity of the heart, for example, pulseless electrical activity
produces an ECG that should pump blood but no pulses are felt (and
constitutes a medical emergency and CPR should be performed).
 Ventricular fibrillation produces an ECG but is too dysfunctional to produce a
life-sustaining cardiac output. Certain rhythms are known to have good cardiac
output and some are known to have bad cardiac output. Ultimately, an
echocardiogram or other anatomical imaging modality is useful in assessing the
mechanical function of the heart.
 Like all medical tests, what constitutes "normal" is based on population studies.
The heart rate range of between 60 and 100 beats per minute (bpm) is
considered normal since data shows this to be the usual resting heart rate.

Classification Angle Notes
Normal −30° to 105° Normal
Left axis deviation −30° to −90°
May indicate
left ventricular hypertrophy,
left anterior fascicular block, or an
old inferior STEMI
Right axis deviation +105° to +180°
May indicate
right ventricular hypertrophy,
left posterior fascicular block, or
an old lateral STEMI
Indeterminate axis +180° to −90°
Rarely seen; considered an
'electrical no-man's land'
Axis: The heart has several axes, but the most common by far is the axis of the QRS complex (references to "the axis" imply the
QRS axis). Each axis can be computationally determined to result in a number representing degrees of deviation from zero, or it can
be
categorized into a few types.
The QRS axis is the general direction of the ventricular depolarization wave front (or mean electrical vector) in the frontal plane.
It is often sufficient to classify the axis as one of three types: normal, left deviated, or right deviated. Population data shows that
a normal QRS axis is from −30° to 105°, with 0° being along lead I and positive being inferior and negative being superior
(best understood graphically as the hexaxial reference system).
Beyond +105° is right axis deviation and beyond −30°
is left axis deviation (the third quadrant of −90° to −180° is very rare and is an indeterminate axis).
A shortcut for determining if the QRS axis is normal is if the QRS complex is mostly positive in lead I and lead II (or lead I and aVF if
+90° is the upper limit of normal). The normal QRS axis is generally down and to the left, following the anatomical orientation of the
heart within the chest. An abnormal axis suggests a change in the physical shape and orientation of the heart or a defect in its
conduction system that causes the ventricles to depolarize in an abnormal way.
The extent of a normal axis can be +90° or 105° depending on the source.

Amplitudes and intervals
All of the waves on an ECG tracing and the intervals between them have a
predictable time duration, a range of acceptable amplitudes (voltages), and a typical
morphology. Any deviation from the normal tracing is potentially pathological and
therefore of clinical significance.
For ease of measuring the amplitudes and intervals, an ECG is printed on graph paper
at a standard scale: each 1 mm (one small box on the standard ECG paper) represents
40 milliseconds of time on the x-axis, and 0.1 millivolts on the y-axis.

Feature Description Pathology Duration
P wave
The P wave represents
depolarization of the
atria. Atrial
depolarization spreads
from the SA node
towards the AV node,
and from the right
atrium to the left
atrium.
The P wave is typically
upright in most leads
except for aVR; an
unusual P wave axis
(inverted in other leads)
can indicate an
ectopic atrial pacemaker
. If the P wave is of
unusually long duration,
it may represent atrial
enlargement. Typically
a large right atrium gives
a tall, peaked P wave
while a large left
atrium gives a two-
humped bifid P wave.
<80 ms

PR interval
The PR interval is measured
from the beginning of the P
wave to the beginning of the
QRS complex. This interval
reflects the time the electrical
impulse takes to travel from the
sinus node through the AV
node.
A PR interval shorter than 120
ms suggests that the electrical
impulse is bypassing the AV
node, as in
Wolf-Parkinson-White syndrome
. A PR interval consistently
longer than 200 ms diagnoses
first degree atrioventricular block
. The PR segment (the portion
of the tracing after the P wave
and before the QRS complex) is
typically completely flat, but
may be depressed in pericarditis
.
120 to 200 ms
Feature Description Pathology Duration

QRS complex
The QRS complex represents the
rapid depolarization of the right
and left ventricles. The ventricles
have a large muscle mass
compared to the atria, so the
QRS complex usually has a much
larger amplitude than the P
wave.
If the QRS complex is wide
(longer than 120 ms) it suggests
disruption of the heart's
conduction system, such as in
LBBB, RBBB, or ventricular
rhythms such as
ventricular tachycardia.
Metabolic issues such as severe
hyperkalemia, or
tricyclic antidepressant overdose
can also widen the QRS
complex. An unusually tall QRS
complex may represent
left ventricular hypertrophy
while a very low-amplitude QRS
complex may represent a
pericardial effusion or
infiltrative myocardial disease.
80 to 100 ms

J-point
The J-point is the point at
which the QRS complex
finishes and the ST segment
begins.
The J-point may be elevated as
a normal variant. The
appearance of a separate J wave
or Osborn wave at the J-point is
pathognomonic of hypothermia
or hypercalcemia.[33]
ST segment
The ST segment connects the
QRS complex and the T wave;
it represents the period when
the ventricles are depolarized.
It is usually isoelectric, but may
be depressed or elevated with
myocardial infarction or
ischemia. ST depression can
also be caused by LVH or
digoxin. ST elevation can also
be caused by pericarditis,
Brugada syndrome, or can be a
normal variant (J-point
elevation).
T wave
The T wave represents the
repolarization of the ventricles.
It is generally upright in all
leads except aVR and lead V1.
Inverted T waves can be a sign
of myocardial ischemia,
left ventricular hypertrophy,
high intracranial pressure, or
metabolic abnormalities.
Peaked T waves can be a sign
of hyperkalemia or very
early myocardial infarction.
16

Corrected QT interval(QTc)
The QT interval is measured
from the beginning of the
QRS complex to the end of
the T wave. Acceptable ranges
vary with heart rate, so it
must be corrected to the QTc
by dividing by the square root
of the RR interval.
A prolonged QTc interval is a
risk factor for ventricular
tachyarrhythmias and sudden
death. Long QT can arise as
a genetic syndrome, or as a
side effect of certain
medications. An unusually
short QTc can be seen in
severe hypercalcemia.
<440 ms
U wave
The U wave is hypothesized to
be caused by the
repolarization of the
interventricular septum. It
normally has a low amplitude,
and even more often is
completely absent.
If the U wave is very
prominent, suspect
hypokalemia, hypercalcemia
or hyperthyroidism.[34]

A pacemaker is a small, battery-operated device. This device
senses when your heart is beating irregularly or too slowly. It
sends a signal to your heart that makes your heart beat at the
correct pace.

 Newer pacemakers weigh as little as 1 ounce (28 grams). Most pacemakers have 2 parts:
 The generator contains the battery and the information to control the heartbeat.
 The leads are wires that connect the heart to the generator and carry the electrical messages to the
heart.
 A pacemaker is implanted under the skin. This procedure takes about 1 hour in most cases. You
will be given a sedative to help you relax. You will be awake during the procedure.
 A small incision (cut) is made. Most often, the cut is on the left side (if you are right handed) of the
chest below your collarbone. The pacemaker generator is then placed under the skin at this
location. The generator may also be placed in the abdomen, but this is less common. A new
"leadless" pacemaker is a self-contained unit that is implanted in the right ventricle of the heart.
 Using live x-rays to see the area, the doctor puts the leads through the cut, into a vein, and then
into the heart. The leads are connected to the generator. The skin is closed with stitches. Most
people go home within 1 day of the procedure.
 There are 2 kinds of pacemakers used only in medical emergencies. They are:
 Transcutaneous pacemakers
 Transvenous pacemakers
 They are not permanent pacemakers.

 Pacemakers may be used for people who have heart problems that cause their heart to
beat too slowly. A slow heartbeat is called bradycardia. Two common problems that
cause a slow heartbeat are sinus node disease and heart block.
 When your heart beats too slowly, your body and brain may not get enough oxygen.
Symptoms may be
 Lightheadedness
 Tiredness
 Fainting spells
 Shortness of breath
 Some pacemakers can be used to stop a heart rate that is too fast (tachycardia) or that is
irregular.
 Other types of pacemakers can be used in severe heart failure. These are called
biventricular pacemakers. They help coordinate the beating of the heart chambers.
 Most biventricular pacemakers implanted today can also work as implantable
cardioverter defibrillators (ICD). ICD restore a normal heartbeat by delivering a larger
shock when a potentially deadly fast heart rhythm occurs.

DEFIBRILLATORS
 Defibrillation is a treatment for life-threatening cardiac dysrhythmias,
specifically ventricular fibrillation (VF) and non-perfusing ventricular tachycardia (VT).
A defibrillator delivers a dose of electric current (often called a counter shock) to
the heart. Although not fully understood, this would depolarize a large amount of
the heart muscle, ending the dysrhythmia. Subsequently, the body's natural
pacemaker in the sinoatrial node of the heart is able to re-establish normal sinus rhythm.
 In contrast to defibrillation, synchronized electrical cardioversion is an electrical shock
delivered in synchrony to the cardiac cycle. Although the person may still be critically
ill, cardioversion normally aims to end poorly perfusing cardiac dysrhythmias, such
as supraventricular tachycardia.
 Defibrillators can be external, transvenous, or implanted (implantable cardioverter-
defibrillator), depending on the type of device used or needed.[4]
Some external units,
known as automated external defibrillators (AEDs), automate the diagnosis of treatable
rhythms, meaning that lay responders or bystanders are able to use them successfully
with little or no training.

Types of Defibrillators
There are different kinds of defibrillators in use today. They include the manual external
defibrillator, manual internal defibrillator, automated external defibrillator (AED),
implantable cardioverter-defibrillator (ICD), and wearable cardiac defibrillator.
Manual external defibrillator: These defibrillators require more experience and
training to effectively handle them. Hence, they are only common in hospitals and a few
ambulances where capable hands are present. In conjuntion with an ECG, the trained
provider determines the cardiac rhythm and then manually determines the voltage and
timing of the shock—through external paddles—to the patient’s chest.
Manual internal defibrillator: The manual internal defibrillators use internal paddles
to send the electric shock directly to the heart. They are used on open chests, so they are
only common in the operating room. It was invented after 1959.
Automated external defibrillator (AED): These are defibrillators that use
computer technology, thereby making it easy to analyze the heart’s rhythm and effectively
determine if the rhythm is shockable. They can be found in medical facilities, government
offices, airports, hotels, sports stadiums, and schools.

Implantable cardioverter-defibrillator: Another name for
this is automatic internal cardiac defibrillator (AICD). They
constantly monitor the patient’s heart, similar to a pacemaker,
and can detect ventricular fibrillation, ventricular tachycardia,
supraventricular tachycardia, and atrial fibrillation. When an
abnormal rhythm is detected, the device automatically determines
the voltage of the shock to restore cardiac function.
Wearable cardiac defibrillator: Further research was done
on the AICD to bring forth the wearable cardiac defibrillator,
which is a portable external defibrillator generally indicated for
patients who are not in an immediate need for an AICD. This
device is capable of monitoring the patient 24-hours-a-day. It is
only functional when it is worn and sends a shock to the heart
whenever it is needed. However, it is scarce in the market today.

Anatomy & Physiology of Cardiac system with Cardiac Assessment- Diagnostic Investigation

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